The present invention relates to a work vehicle with an exhaust gas diffusing device.

Documents JP 52-152911 (Japanese Unexamined Utility Model Application Publication, Jitsukaishou, No. 52-152911) and JP 24-108817 (Japanese Unexamined Utility Model Application Publication, Jitsukaishou, No. 54-108817) each disclose an exhaust gas diffusing device including, at an end portion of an exhaust pipe, a cylindrical member for diffusing exhaust gas.

Document JP 52-152911 discloses a unit ("muffler cutter") including an attachment pipe and a mixing/discharging pipe attached to the attachment pipe. The mixing/discharging pipe has a diameter larger than that of the exhaust pipe. The mixing/discharging pipe has, at an end portion thereof on the exhaust pipe side, a plurality of introduction openings for introducing outside air. The mixing/discharging pipe contains a freely rotatable fan.

Attaching the attachment pipe to the back end of the exhaust pipe results in the mixing/discharging pipe overlapping with the back end of the exhaust pipe. The mixing/discharging pipe receives exhaust gas as well as outside air, diffuses the exhaust gas by means of rotation of the fan at an intermediate portion of the mixing/discharging pipe to reduce the concentration of the exhaust gas, and then discharges the exhaust gas.

Document JP 24-108817 discloses a unit ("diffuser") including a cylinder having an elliptical cross section and an exhaust pipe connection fitting attached to an end portion of the cylinder. The cylinder has first outside air introduction openings, and contains a pair of guide vanes facing each other.

The pair of guide vanes define a nozzle therebetween. The cylinder has second outside air introduction openings in the vicinity of the nozzle. Connecting the exhaust pipe connection fitting to the exhaust pipe allows exhaust gas from the exhaust pipe to be introduced into the cylinder. The exhaust gas thus introduced increases its flow speed at the nozzle. The cylinder introduces outside air through the second outside air introduction openings as well as the first outside air introduction openings to cool the exhaust gas before discharging it.

Document US 4 331 213A pertains to an exhaust gas control system havin a guiding pipe with a proximal inlet end for connecting to a distal end of an engine exhaust pipe. An expanding portion of the guiding pipe has a central rearward expanding cone and spiraling blades extending between the cone and the walls of the expanding portion. The expanding portion is followed by an axially decreasing chamber and then an axially increasing chamber to the distal opening. A duct is supported on radial vanes around the latter chambers. The duct has a forward opening slightly rearward of a maximum cross-sectional dimension of the guiding pipe and has an outlet positioned rearward of the distal opening of the guiding pipe.

Document FR 2 689 577 A1 discloses a booster consisting of a convergent pipe situated at a distance from a circuit intake so that the flow of air or gas passing through the pipe is first compressed and allowed to expand, creating a supplementary flow of outside air which is drawn into the intake. The convergent pipe forms a truncated cone set at a variable distance from the circuit intake.

In document US 2010 / 000 205 A1, an exhaust gas cooling apparatus and method for cooling an exhaust gas is disclosed. The exhaust cooling apparatus has a first fluid conduit and a variable nozzle extending from the first fluid conduit. The variable nozzle is disposed in an inlet end of a second fluid conduit, wherein the variable nozzle has at least two dissimilar materials adjacent to each other and a fluid inlet opening is located between an outer periphery of the variable nozzle and an inner surface of the inlet end of the second fluid conduit.

Document KR 2014 0 096 709 A relates to an exhaust flow rate increasing device for a vehicle, in which air outside the front end of an exhaust pipe is induced by the flow of gas exhausted through the exhaust pipe as the vehicle progresses and the outside air is faster than the flow of the exhaust gas.

In document GB 2 513 187 A, a diffuser assembly for cooling a hot exhaust gas comprises an exhaust gas feeder unit and a tubular exhaust gas discharge unit having an upstream end mounted on the feeder unit such that there is a clearance space between the inner surface of said upstream end and the outer surface of a body portion of the feeder unit.

Document US 2005/205355 A1 discloses a tailpipe of an automotive vehicle comprising a front tube coupled to a muffler, the front tube including two flared ends and a neck having a plurality of apertures, a rear tube having a flared end, an outer venturi tube surrounding a rear portion of the front tube and the whole rear tube, the outer tube including a flared front end, a cylindrical section, an enlarged section, and a rear section having an inward extending rim at an opening thereof, and a plurality of twisted blades equally spaced apart around the rear tube and connected to the front, the rear, and the outer tubes, each blade having a plurality of apertures. Stream of exhaust from the muffler entering into the neck is divided into a number of components prior to forming whirlwind after leaving the tailpipe.

A work vehicle such as a tractor including a diesel engine, for example, may include a diesel particulate filter (DPF) to clean exhaust gas. Including a DPF as such, however, involves the concern that exhaust gas discharged from the engine may be heated up as a result of heat generation through the cleaning process and be discharged without being cooled sufficiently.

Such high-temperature exhaust gas may be cooled with use of, for example, the diffusion technique disclosed in documents JP 52-152911 or JP 24-108817. The technique of document JP 52-152911, however, mixes exhaust gas with outside air at an intermediate portion of the mixing/discharging pipe before discharging the exhaust gas. The mixing/discharging pipe is long as a result. The technique of document JP 24-108817 uses a pair of guide vanes to define a throttle nozzle. The pair of guide vanes thus partially block the flow of exhaust gas.

The above circumstances have led to a demand for an exhaust gas diffusing device that cools exhaust gas from an exhaust pipe, that does not block the flow of exhaust gas, and that does not require an increased distance for exhaust gas and outside air to be mixed with each other.

A work vehicle with an exhaust gas diffusing device according to claim 1 is provided.

The above configuration allows exhaust gas from the exhaust pipe to enter the outside air mixing cylinder together with outside air, and causes the exhaust gas and the outside air to flow as guided by the air director. This promotes mixing of exhaust gas with outside air. Further, the air director is disposed either in the exhaust pipe or at a position on the outside air mixing cylinder which position is upstream in the direction in which exhaust gas flows. This makes it possible to not only mix exhaust gas with outside air but also dissipate heat without the need to increase the distance over which exhaust gas and outside air flow through the space inside the outside air mixing cylinder from its upstream portion to its downstream portion.

The above configuration thereby provides an exhaust gas diffusing device that cools exhaust gas from an exhaust pipe, that does not block the flow of exhaust gas, and that does not require an increased distance for exhaust gas and outside air to be mixed with each other.

The exhaust gas diffusing device is arranged such that the at least one air director is disposed only in the exhaust pipe.

With the above configuration, the air director is disposed in the exhaust pipe only. This simple configuration allows exhaust gas to be guided into the outside air mixing cylinder.

The exhaust gas diffusing device is arranged such that the at least one air director is disposed at the discharge-side end portion of the exhaust pipe.

With the above configuration, the air director is disposed at the discharge-side end portion of the exhaust pipe. This allows exhaust gas flowing in a direction defined by the air director to directly enter the outside air mixing cylinder past the air director.

The exhaust gas diffusing device may further be arranged such that the exhaust gas diffusing device has a gap between the discharge-side end portion and an end portion of the outside air mixing cylinder which end portion is upstream in the direction in which the exhaust gas flows.

The above configuration causes a negative pressure when exhaust gas flows from the exhaust pipe into the outside air mixing cylinder. The negative pressure in turn draws in outside air through the gap into the outside air mixing cylinder.

The exhaust gas diffusing device is arranged such that the at least one air director does not coincide with the outside air mixing cylinder as viewed in a direction orthogonal to the direction in which the exhaust gas flows.

The above configuration involves a gap between the air director on the exhaust pipe and the outside air mixing cylinder which gap allows outside air to pass therethrough. The air director thus does not prevent outside air from being drawn in.

The exhaust gas diffusing device may further be arranged such that the at least one air director is oriented to guide the exhaust gas in such a direction that the exhaust gas comes into contact with an inner surface of the outside air mixing cylinder.

With the above configuration, the air director guides exhaust gas toward the inner surface of the outside air mixing cylinder. This allows exhaust gas to come into contact with the inner surface of the outside air mixing cylinder for efficient heat dissipation. In particular, guiding exhaust gas toward the inner surface of the outside air mixing cylinder causes the exhaust gas to whirl along the inner surface, thereby promoting the mixing of exhaust gas with outside air.

The exhaust gas diffusing device may further be arranged such that the at least one air director includes a plurality of air directors arranged in point symmetry to each other as viewed in the direction in which the exhaust gas flows.

With the above configuration, the plurality of air directors guide exhaust gas uniformly and cause the exhaust gas to whirl, thereby efficiently mixing exhaust gas with outside air.

Fig. 1

is a side view of a tractor including an exhaust gas diffusing device.

Fig. 2

is an exploded perspective view of an exhaust pipe, an intermediate cylinder, and air directors.

Fig. 3

is a perspective view of an exhaust pipe, air directors attached thereto, and an outside air mixing cylinder.

Fig. 4

is a side view of an exhaust pipe, air directors attached thereto, and an outside air mixing cylinder.

Fig. 5

is a cross-sectional view taken along line V-V in Fig. 4.

Fig. 6

is a perspective view of an exhaust pipe and an outside air mixing cylinder according to alternative embodiment (a).

Fig. 7

is a cross-sectional view taken along line VII-VII in Fig. 6.

Fig. 8

is a perspective view of an exhaust pipe and an outside air mixing cylinder according to alternative embodiment (b).

Fig. 9

is a cross-sectional view taken along line IX-IX in Fig. 8.

Fig. 10

is a perspective view of an exhaust pipe and an outside air mixing cylinder according to alternative embodiment (c).

Fig. 11

is a cross-sectional view of an exhaust pipe and an outside air mixing cylinder according to alternative embodiment (d).

The description below deals with an embodiment of the present invention with reference to drawings.

Fig. 1 illustrates a tractor T as a work vehicle. The tractor T includes a hood 1 at a front portion thereof, and also includes inside the hood 1 a diesel engine 2, a radiator 3, an air cleaner 4, and a diesel particulate filter (DPF) cleaning device 5 for cleaning exhaust gas.

The tractor T also includes an exhaust pipe 6, a body frame 7, and an exhaust gas diffusing device A. The exhaust gas diffusing device A includes an outside air mixing cylinder 11 at such a position on a side of the body frame 7 as to receive exhaust gas from the exhaust pipe 6. The exhaust gas diffusing device A allows exhaust gas of the engine 2 cleaned by the cleaning device 5 and thereby heated to be mixed with outside air to be cooled.

The exhaust pipe 6 is positioned at a front portion of the vehicle body and so oriented as to discharge exhaust gas in an obliquely downward direction. The outside air mixing cylinder 11 is so oriented as to send out exhaust gas in the direction of the exhaust pipe 6.

As illustrated in Figs. 1 to 5, the exhaust gas diffusing device A includes an outside air mixing cylinder 11, an intermediate cylinder 12, and air directors 13 supported by the intermediate cylinder 12. The outside air mixing cylinder 11, the intermediate cylinder 12, and the air directors 13 are each made of, for example, a heat-resistant steel material or a stainless steel material.

The exhaust pipe 6 has a cylindrical axis X virtually extending through the center of the pipe. The outside air mixing cylinder 11 has its center extending coaxially with the cylindrical axis X. The intermediate cylinder 12 is fitted around the exhaust pipe 6 and fixed thereto with use of a plurality of bolts 15. The intermediate cylinder 12 is provided with a pair of support frames 14 fixed thereto. The air directors 13 are integral with one of the support frames 14 (detailed later).

With the above configuration, the air directors 13 are at a discharge-side end portion 6E of the exhaust pipe 6. The air directors 13 are, in other words, provided for the exhaust pipe 6 only.

As illustrated in Fig. 5, the outside air mixing cylinder 11 is a cylindrical member having an inner diameter D2 larger than the outer diameter D1 of the discharge-side end portion 6E of the exhaust pipe 6. The outside air mixing cylinder 11 is held in place by the body frame 7 of the tractor T. The intermediate cylinder 12 is fitted around and fixed to the discharge-side end portion 6E of the exhaust pipe 6, and holds the air directors 13 in place.

The outside air mixing cylinder 11 may alternatively be held in place by (i) the exhaust pipe 6 with, for example, a bracket in-between or (ii) the intermediate cylinder 12 fitted around and fixed to the exhaust pipe 6.

As illustrated in Fig. 4, placing the exhaust pipe 6 and the outside air mixing cylinder 11 in position results in a gap G being formed between the discharge-side end portion 6E of the exhaust pipe 6 and the upstream end portion 11E of the outside air mixing cylinder 11. The present embodiment is arranged such that the air directors 13 are in a space inside the discharge-side end portion 6E of the exhaust pipe 6 and that the air directors 13 and the outside air mixing cylinder 11 are so positioned as not to coincide with each other as viewed in the direction orthogonal to the direction in which exhaust gas flows (that is, in the direction in which Fig. 4 is viewed).

Fig. 4 illustrates a case of the discharge-side end portion 6E and the corresponding end portion of the intermediate cylinder 12 coinciding with each other. In a case where, for instance, the intermediate cylinder 12 protrudes from the discharge-side end portion 6E of the exhaust pipe 6, the gap G is formed between the end portion of the intermediate cylinder 12 and the upstream end portion 11E of the outside air mixing cylinder 11.

As illustrated in Figs. 2 to 5, the two air directors 13 are, for example, press-worked to be integral with a first one of the pair of support frames 14, and are inclined in respective directions opposite to each other. The two air directors 13 are, as illustrated in Fig. 5, in point symmetry to each other as viewed in the direction in which exhaust gas flows from the exhaust pipe 6 (that is, in the direction of the cylindrical axis X).

As illustrated in Fig. 2, a second one of the pair of support frames 14 has a depression 14b at a central position in its length direction (that is, in the radial direction of the intermediate cylinder 12). Engaging the first support frame 14 with the depression 14b and welding the first support frame 14 to the second support frame 14 for fixation results in the pair of support frames 14 being orthogonal to each other and radially crossing the intermediate cylinder 12 as viewed in the direction of the cylindrical axis X.

The support frames 14 each include, at respective opposite ends thereof, engagement sections 14a each in the form of a bend in the direction of the cylindrical axis X. The support frames 14 are welded and fixed to the outer surface of the intermediate cylinder 12 with the engagement sections 14a in contact with an outer edge of the intermediate cylinder 12.

The above configuration involves a gap between the radially outer end of each of the pair of air directors 13 on the first support frame 14 and the inner surface of the intermediate cylinder 12. The gap receives the discharge-side end portion 6E of the exhaust pipe 6 when the intermediate cylinder 12 is fitted around the exhaust pipe 6. This allows the air directors 13 to be inside the exhaust pipe 6 as viewed in the direction orthogonal to the direction in which exhaust gas flows (that is, in the direction orthogonal to the cylindrical axis X).

The above configuration causes exhaust gas from the exhaust pipe 6 to come into contact with the pair of air directors 13 immediately before being discharged from the discharge-side end portion 6E of the exhaust pipe 6 and then be sent out toward the inner surface of the outside air mixing cylinder 11 as illustrated in Fig. 4. Orienting the pair of air directors 13 in a particular manner causes exhaust gas to, after coming into contact with the air directors 13, be sent out toward the inner surface of the outside air mixing cylinder 11 such that the exhaust gas whirls along the inner surface of the outside air mixing cylinder 11 (that is, about the cylindrical axis X as the center). The air directors 13 configured as above do not block the flow of exhaust gas, and allow exhaust gas to flow with a reduced pressure loss.

As described above, the gap G is between the exhaust pipe 6 and the outside air mixing cylinder 11. The gap G causes a negative pressure when exhaust gas flowing along the cylindrical axis X passes through the gap G. The negative pressure in turn causes outside air to enter the outside air mixing cylinder 11 through an outside air introducing section F. The air directors 13, which guide exhaust gas toward the inner surface of the outside air mixing cylinder 11, promote mixing of exhaust gas with outside air introduced through the outside air introducing section F.

The above configuration allows exhaust gas to be diffused to promote mixing of exhaust gas with outside air without requiring an increased distance for exhaust gas and outside air to be mixed with each other inside the outside air mixing cylinder 11. This makes it possible to reduce the length of the outside air mixing cylinder 11 (that is, the dimension thereof along the cylindrical axis X) and discharge cooled exhaust gas from the discharge-side end portion. The above configuration, which does not require the outside air mixing cylinder 11 to be long as such, does not require the exhaust gas diffusing device A to be large-sized.

The outside air mixing cylinder 11 has an outer surface in constant contact with outside air. Further, exhaust gas mixed with outside air as described above flows through the outside air mixing cylinder 11 while in contact with its inner surface in such a manner as to whirl along the inner surface. This further promotes heat dissipation, thereby allowing suitable heat dissipation.

The present invention may alternatively be arranged as below other than the embodiment described above. Any member below that is identical in function to a particular member described for the above embodiment has the same reference sign as that particular member.

1. (a) The present invention may be modified as illustrated in Figs. 6 and 7 by (i) cutting, in an end portion of the intermediate cylinder 12, a pair of slits parallel to the cylindrical axis X, (ii) bending, toward the center of the intermediate cylinder 12, portions of the intermediate cylinder 12 that are in the vicinity of the slits such that those portions are inclined to guide exhaust gas (that is, to serve as air directors 13), and (iii) fitting the intermediate cylinder 12 around the exhaust pipe 6 to fix the intermediate cylinder 12 thereto.
   This alternative embodiment (a) involves simply cutting slits in an end portion of the intermediate cylinder 12 and bending portions thereof to form air directors 13. This eliminates the need to additionally include dedicated air directors 13, and reduces the number of necessary parts. Alternative embodiment (a), similarly to the embodiment described above, causes exhaust gas to whirl along the inner surface of the outside air mixing cylinder 11 while in contact therewith for suitable heat dissipation.
   Alternatively embodiment (a) may be varied by, for instance, cutting slits in the back end of the exhaust pipe 6 and bending portions thereof to form air directors 13.
2. (b) The present invention may be modified as illustrated in Figs. 8 and 9 by (i) preparing a plate-shaped member 21 including bent end portions as a pair of air directors 13, (ii) inserting the plate-shaped member 21 into the intermediate cylinder 12 such that the plate-shaped member 21 is oriented radially, (iii) welding or otherwise fixing the plate-shaped member 21 to the intermediate cylinder 12, and (iv) inserting the intermediate cylinder 12 into the discharge-side end portion 6E of the exhaust pipe 6 to fix the intermediate cylinder 12 thereto.
   This alternative embodiment (b), which includes a plate-shaped member 21 fixed inside the intermediate cylinder 12, allows air directors 13 to be formed easily. Alternative embodiment (b), similarly to the embodiment described above, causes exhaust gas to whirl along the inner surface of the outside air mixing cylinder 11 while in contact therewith for suitable heat dissipation.
3. (c) The present invention may be modified as illustrated in Fig. 10 such that only one of the pair of support frames 14 for the embodiment described above includes engagement sections 14a and that air directors 13 are formed on the other support frame 14. The pair of support frames 14 for this embodiment are welded and fixed to each other at a portion at which the pair of support frames 14 cross each other.
   This alternative embodiment (c) allows size reduction of the support frame 14 on which the air directors 13 are formed.
4. (d) The present invention may be modified as illustrated in Fig. 11 by including air directors 13 at a position inside the outside air mixing cylinder 11 which position is upstream in the direction in which exhaust gas flows. The pair of air directors 13 for this embodiment are formed on an internal plate 23 welded or otherwise fixed inside the outside air mixing cylinder 11. The pair of air directors 13 coincide, as viewed in the direction of the cylindrical axis X, with the path into which exhaust gas is sent out from the exhaust pipe 6.
   This alternative embodiment (d), similarly to the embodiment described above, causes exhaust gas to whirl along the inner surface of the outside air mixing cylinder 11 while in contact therewith for suitable heat dissipation.
5. (e) The number of air directors 13 is not limited to two, but may be three or more. Further, the air directors 13 may be disposed both for the exhaust pipe 6 and inside the outside air mixing cylinder 11.
6. (f) The exhaust gas diffusing device A does not necessarily have a gap G between the discharge-side end portion 6E of the exhaust pipe 6 and the outside air mixing cylinder 11. The discharge-side end portion 6E of the exhaust pipe 6 and the outside air mixing cylinder 11 may, for instance, slightly overlap with each other as viewed in the direction orthogonal to the cylindrical axis X.
7. (g) The air directors 13 do not necessarily protrude from the discharge-side end portion 6E of the exhaust pipe 6. This configuration of the air directors 13 not protruding from the discharge-side end portion 6E of the exhaust pipe 6 may be combined with the configuration of the exhaust gas diffusing device A having no gap G between the discharge-side end portion 6E of the exhaust pipe 6 and the outside air mixing cylinder 11.

The present invention is applicable to exhaust gas diffusing devices.

2

Engine

6

Exhaust pipe

6E

Discharge-side end portion

11

Outside air mixing cylinder

12

Intermediate cylinder

11E

Upstream end portion

13

Air director

14

Support frame

A

Exhaust gas diffusing device

G

Gap

D1

Outer diameter

D2

Inner diameter

X

Cylindrical axis